Intracellular delivery of materials is a challenge. Existing technologies that rely on nanoparticles, electrical fields, pore-forming chemicals, etc. are capable of delivering some materials to certain cell types but often in an indiscriminant fashion with regards to the physical properties of the target cell. By developing selective delivery methods dependent on the physical properties of the target cells, one could exert more robust control in delivery activity for research, diagnostic or therapeutic applications. For example, Circulating tumor cells (CTCs) are tumor cells found in the bloodstream, believed to mediate metastasis, or the spread of cancer, to distant sites in the body. Approximately 90% of human deaths from cancer are due to metastasis. Identification and characterization of CTCs could be the key to understanding, treating, or preventing metastatic cancer. Moreover these cells are known to have different physical properties compared to the surrounding blood cells.